1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer which forms images using a reusable unit containing expendable materials such as toner, ink or a photoconductive material, and more particularly to a reusable unit and an image forming apparatus using the reusable unit which realize less emission of wastes and excellent imaging quality.
2. Description of the Related Art
An electrophotographic image forming apparatus (such as a laser printer, a copying machine) has been known as an apparatus for forming images using toner. Such a image forming apparatus generally comprises a photoconductive unit and an image developing unit each of which is detachably installed in a main component of an image forming apparatus. The photoconductive unit comprises a photoconductive element on which electrostatic latent images are formed. The image developing unit develops the electrostatic latent images.
Generally, the photoconductive unit is replaced with a new one and dumped when the photoconductive element no longer works. The image developing unit is also replaced with a new one and damped when the toner in it is fully exhausted. The new unit is usually supplied by the manufacturer of the image forming apparatus.
Because such units are expendable, not only the manufacturer of the image forming apparatus but also third parties produce such the units. Since those units produced by the third parties are not genuine products, some of them have crude quality which may damage the image forming apparatus.
As described above, those units are designed as expendable products to be dumped. However, some of the wasted units have been resold for reuse nowadays. The resellers collect the wasted units and refill toner in the image developing unit or replace the photoconductive element in the photoconductive unit.
Such reselling activity is helpful for less emission of wastes. However, the toner to be refilled or the photoconductive element to be replaced is not a genuine product because they are produced by third parties. That is, some of the resold products have crude quality like the above mentioned copy products. The crude quality of the resold units may cause quality deterioration of resultant images. Moreover, the image forming apparatus may be damaged by scattered toner, irregularly remaining toner on a fixing roller, and the like. In practice, it is difficult to judge whether such problems are caused by the image forming apparatus or the non-genuine unit installed therein.
If the cause of the problem is unknown, it is unclear who should take responsibility for the problem. In such a case, the manufacturer of the image forming apparatus has no means to solve the problem. And if the problem remains unsolved, and similar problems occur in following products, users may come to believe that the image forming apparatus itself is the cause of the problem. Such a misunderstanding may affect the manufacturer's reputation.
U.S. Pat. No. 5,761,566 discloses a technique which inhibits an irregular cartridge from being used. According to the disclosure in this patent, an uneven patterned logo mark is formed on a surface of a cartridge which contains expendable material. The logo mark is incorporated with a resin frame. And detection switches are provided in an image forming device to detect projected portions of the logo mark, so that it can be determined whether the cartridge is genuine or not.
However, manufacturing such a cartridge is expensive because forming such a logo mark is complex work. Moreover, the disclosed technique will be helpful for inhibiting the above mentioned copy products from being used, however, it is not effective in preventing use of the reused products, because they use genuine cartridges whose contents are replaced. As a result, problems caused by such reused products will be unsolved.